[R] adding NA to "subset"

[Duncan Murdoch]

Sherri Heck wrote:
> Hi All-
>
> I have a data set (spdco2)
>
>  > spdco2
>       [,1] [,2]     [,3]
>  [1,]    1  5.4 382.4212
>  [2,]    2  5.1 383.0315
>  [3,]    3  4.8 383.9520
>  [4,]    4  4.7 384.4376
>  [5,]    5  4.7 384.5929
>  [6,]    6  4.4 384.8864
>  [7,]    7  4.1 385.2156
>  [8,]    8  3.8 385.2919
>  [9,]    9  3.7 385.5925
> [10,]   10  3.9 385.6801
>
>
> I am subsetting it to output when [,2] is >= 4.7 . 
>
> x<-subset(spdco2,spdco2[,2]>=4.7)
>
> This works, but I would like to add 'NA' to the data that it does 
> exclude based on my subset criteria.  I have searched through the 
> archives and two R books, but I cannot figure out how to add the NA.
> Any suggestions would be appreciated-
Use is.na():

x <- subset(spdco2, spdco2[,2] >= 4.7 | is.na(spdco2[,2]))

Make sure that the inclusion or exclusion of the row can be computed:  
TRUE | NA is TRUE, but FALSE | NA is NA.

Duncan Murdoch

Duncan Murdoch